The primary objective of this study is to assess the effect of three anticoagulans (sodium citrate, heparin and PPACK) on the assessment of platelet inhibition induced in-vitro by GP IIb/IIIa antagonist. Platelet function will be assessed by platelet-rich plasma (PRP) aggregation, whole blood aggregation, platelet GP IIb/IIIa receptor occupancy, and platelet-adhesion.